package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.CacheClient;
import com.hmdp.utils.RedisConstants;
import com.hmdp.utils.RedisData;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;
import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.*;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Resource
    private StringRedisTemplate stringRedisTemplate;

    @Resource
    private CacheClient cacheClient;


    public Result queryById(Long id) {
        //缓存穿透
      // Shop shop = cacheClient.queryWithPassThrough(CACHE_SHOP_KEY,id,Shop.class,this::getById,CACHE_SHOP_TTL,TimeUnit.MINUTES);

        //互斥锁解决缓存击穿
      //  Shop shop = queryWithMutex(id);
        //逻辑过期解决缓存击穿问题
        Shop shop = cacheClient.queryWithLogicalExpire
                (CACHE_SHOP_KEY,id,Shop.class,this::getById,CACHE_SHOP_TTL,TimeUnit.MINUTES);
        if (shop == null)
        {
            return Result.fail("店铺不存在!");
        }
        //返回
        return Result.ok(shop);

    }
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    public Shop queryWithLogicalExpire(Long id)
    {
        String key = CACHE_SHOP_KEY + id;
        //1从redis查询商户缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2判断是否存在
        if (StrUtil.isBlank(shopJson)) {
            //3不存在，返回空
            return null;
        }
        //4 命中，需要先把json反序列化对象
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        Shop shop = JSONUtil.toBean((JSONObject) redisData.getData(), Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5. 判断是否过期
        if (expireTime.isAfter(LocalDateTime.now()))
        {
            //5.1未过期，直接返回店铺信息
            return  shop;
        }
        //5.2 已过期，需要缓存重建
        //6. 缓存重建
        //6.1 获取互斥锁
        String lockKey=LOCK_SHOP_KEY+id;
        boolean isLock = tryLock(lockKey);
        //6.2判断是否获取锁
        if (isLock)
        {
            //6.3 TODO 成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() ->{
                try {
                    //重建缓存
                    this.saveShop2Redis(id,20L);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }finally {
                    //释放锁
                    unLock(lockKey);
                }
            });
        }
        //6.4 返回过期的商品信息
        return shop;
    }


    //互斥锁具体实现
    public Shop queryWithMutex(Long id)
    {
        String key = CACHE_SHOP_KEY + id;
        //1从redis查询商户缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2判断是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            //3存在，直接返回,转成Java对象返回
            return JSONUtil.toBean(shopJson, Shop.class);

        }
        //判断是否为null,前面isNotblank只判断里面有值，这里如果不为空就为空串
        if (shopJson != null)
        {
            return null;
        }
        //4实现缓存重建
        //4.1获取互斥锁
        String lockKey=LOCK_SHOP_KEY+id;
        Shop shop = null;
        try {
            boolean isLock = tryLock(lockKey);
            //4.2判断是否获取成功
            if (!isLock)
            {
                //4.3失败，则休眠重试
                Thread.sleep(50);
                //重试，递归
                return queryWithMutex(id);
            }
            //4.4成功,根据id查询数据库
            shop = getById(id);
            // TODO 模拟重建的延迟
            Thread.sleep(200);
            //5不存在返回错误
            if (shop == null) {
                //5.1将空值写入redis
                stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL, TimeUnit.MINUTES);
                //5.2返回错误信息
                return null;
            }
            //6存在，写入redis，返回
            stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }finally {
            //7释放互斥锁
            unLock(lockKey);
        }
        //8返回
        return shop;
    }
    //获取互斥锁
    private  boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }
    //释放锁
    private  void  unLock(String key)
    {
        stringRedisTemplate.delete(key);
    }

    //缓存穿透代码
    public Shop queryWithPassThrough(Long id)
    {
        String key = CACHE_SHOP_KEY + id;
        //1从redis查询商户缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2判断是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            //3存在，直接返回,转成Java对象返回
           return JSONUtil.toBean(shopJson, Shop.class);

        }
        //判断是否为null,前面isNotblank只判断里面有值，这里如果不为空就为空串
        if (shopJson != null)
        {
            return null;
        }
        //4不存在,根据id查询数据库
        Shop shop = getById(id);
        //5不存在返回错误
        if (shop == null) {
            //5.1将空值写入redis
            stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL, TimeUnit.MINUTES);
            //5.2返回错误信息
            return null;
        }
        //6存在，写入redis，返回
        stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);
        return shop;
    }

    //逻辑过期(商品预热)
    public void  saveShop2Redis(Long id,Long expireSeconds) throws InterruptedException {
        //1.查询店铺数据
        Shop shop = getById(id);
        // TODO 延迟测试
        Thread.sleep(200);
        //2.封装逻辑过期时间
        RedisData redisData = new RedisData();
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));
        //3.写入Redis
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id,JSONUtil.toJsonStr(redisData));

    }
    @Override
    @Transactional
    public Result update(Shop shop) {
        Long id = shop.getId();
        if (id == null)
        {
            return Result.fail("店铺id不能为空");
        }
        //1更新数据库
        updateById(shop);
        //2删除缓存
        stringRedisTemplate.delete(CACHE_SHOP_KEY + id);
        return Result.ok();

    }
}
